Dewatering and water management
The unique, underground nature of the Ghaghoo mine presents a number of challenges. One of the major issues the mine faces is the volume of groundwater discovered during underground tunnelling activities.
In early 2015, a study on the responsible management of the groundwater was finalised with several options presented, including the use of evaporation ponds, forced evaporation, constructed wetlands, water treatment for domestic consumption and use, water treatment for agricultural irrigation, game watering and finally, aquifer re-injection.
In determining the feasibility of these options, it was necessary to consider a number of factors such as financial viability, environmental care and sustainability, and efficiency. While water is a scarce commodity, the water obtained from underground is generally not suitable for use without significant treatment, which is extremely costly. Thus, consumption, either by humans or game, was not a viable solution. Treatment for agricultural irrigation was less extensive and therefore considerably cheaper, however, transporting the treated water would be expensive due to the remote location of the mine.
Minimising the environmental damage was also a major factor in our study. While game watering was reviewed as an option, the construction of a watering hole would severely alter the present desert-like environment and could have an effect on wildlife migratory patterns, as well as the natural ecological balance of the area of the Central Kalahari Game Reserve in which the mine is located. Wetland construction has the potential for natural water treatment, yet would again be an alteration of the natural environment. One option investigated was controlled evaporation of the water. However, the significant environmental impacts as well as infrastructural costs resulted in this option being disregarded.
After extensive consideration, aquifer re-injection was deemed to be a viable option. Re-injection of groundwater has several major advantages. First, manipulation of head gradients would allow us to have a measure of control over the hydrological flow, thus helping to manage the water on a long-term basis. Secondly, groundwater re-injection is environmentally sustainable and restorative, therefore providing an environmentally friendly aid in the aquifer’s natural decontamination process. And finally, the project presents a financially acceptable option. Operational costs are minimal, and initial infrastructural setup is comparatively feasible. Furthermore, we believe that aquifer re-injection is the most responsible course of action in an environment that experiences water scarcity.
The implementation and operation of the aquifer re-injection pilot project is planned for 2016, with further investigation and monitoring to take place before selecting a long-term management strategy.
|Ghaghoo Diamond Mine,
(Environmental Officer) conducting water quality monitoring.